A widely used terminal for connecting a wire or conductor is the so-called “backwired type”, as seen in FIGS. 1 and 2. The backwired terminal 100 includes, essentially, a screw 102, a current carrying terminal plate 104, and a clamping nut 106. In many such backwired terminals, the terminal plate has a clearance opening to receive the screw, and the screw is threaded into the clamping nut to draw the clamping nut toward the terminal plate when the screw is tightened. In the conventional backwired terminal, the electrical connection is made by inserting the stripped end of an insulation jacketed conductor 108 between the clamping nut and the terminal plate and then tightening the screw to compress the conductor between the clamping nut and the plate. Such backwired terminals are quite popular because of the ease of connecting a conductor to the terminal, and because the terminal assembly can be surrounded with electrically insulating barriers or a housing 110.
Since it is preferable to have the backwire terminals surrounded with electrically insulating barriers, the terminals are generally accessible through the housing by a relatively small rectangular opening therein. The opening is preferably not much larger than the clamping nut. To couple the clamping nut to the terminal, the clamping nut is placed overlying the terminal in the opening immediately adjacent the walls of the housing. Therefore, when the screw is tightened to compress the conductor between the clamping nut and the plate, the clamping nut generally rotates in the direction of the screw due to frictional forces, as shown in FIG. 2.
When the clamping nut rotates, an edge of the clamping nut contacts the wall of the housing, causing a portion, or upwardly extending wall, of the bottom of the housing to be pushed or bow outwardly. This outward movement generally is greatest at the portion of the wall distal from the bottom surface of the housing. In other words, the upwardly extending wall pivots around the portion of the wall proximal to the bottom surface of the housing. This pivoting motion forces the upper portion of the housing away from the lower portion of the housing and creates a gap 112 between the two housing portions adjacent the two clamping nuts.
The gap, or separation, between the two housing portions can adversely affect the performance of the electrical device by allowing the terminal plates 104 to separate and move out of position. If the terminal plates move out of position, the electrical contacts supported by the terminal plates may not line up or make proper contact with each other, causing failure of the electrical device when the device is closed to complete the electrical circuit.
Thus, a need exists to provide an improved electrical device that has terminal plates that limit the internal wiring clamps from turning and therefore prevent separation of the housing.